eandall



0.1L RANDALL.. TELBPHONIG TRANSMITTER.

(No Model.)

Patented Man 25, 1884,

Unirse STATES arent farina,

CHARLES A. RANDALL, OF YORK, N. Y.

TELEPHONIC TRANSMITTER.

SPECIFICATION forming part of Letters Patent No. 295,807, dated March 275, 1884 l l Application filed February 6, 1883. (No model.)

To @Mu/hom it may concern:

Be itknown that I, CHARLEs A. RANDALL, a citizen of the United States, residing at New York, inthe countyand State of New York,

have invented new and useful Improvements in Telephonie Transmitters, of which the following is a specification.`

This inventionrelates to that class of transmitting-telephones in which one of the contact-electrodes is" supported by or in contact with a body of liquid.

In telephones of this class as heretofore constructed, the upper` surface of the electrode-sup-` porting liquid, usually mercury, has been left free, and such transmitters have been found unreliable, on account of the oversensitiveness of the free liquid to pressure,its variations of condition under thermal changes, and the tend-4 ency of .its surface to continue in undulatory or tremulous motion after being moved by the electrode whichis in contact therewith.l

Itis the object of my invention to overcome the disadvantages heretofore attendant upon the use of a' liquid to support or partly suppcrt one of the electrodes of a transmitting-telephone; and to this end it consists in the combination,with one of the electrodes, of a yielding or elastic plate and a body of liquid', the yielding or elastic plate forming the cover to the vessel containing the liquid, which is confined therein under pressure and serves the purpose of regulating the tension of the said plate, as `will `be hereinafter fully described with reference to the accompanying drawing.

In the drawing the figure is a view, mainly in vertical section, of atransmitting-telephone constructed according to my invention.

Referring to the said drawing, the letter A indicates a horizontal vibratory diaphragm, which is held at the edges by the usual clamping-rings. B is the casing, at the top of which the diaphragm is located, and C is a curved mouth-piece arranged to receive `horizontally the sounds" to be transmitted and direct them upon the diaphragm. To the under side of the diaphragmis secured a'central button, D, preferably of carbon,and under the diaphragm is arranged a cup, E, having an elastic top, e, preferably of mica, though it may be made of thin sheet metal or hard rubber, or any other material of a resilient nature. This top is secured to the upper edge or flange of the cup by means of a ring, c', and carbon button D', a portion of which extends downward through the top and into thecup,while the other portion projects above the top and directly under the button D, which is carried by the diaphragm. Through the bottom of the cup E extends a metallic screw, F, havingadiameter about one-third that of the cup; but it may be either larger or smaller than this, as will be understood from its function hereinafter explained. The cup E rests upon a spring-arm, G, which is secured to a bracket, g, attached to the wall of thecasing B, and through a-n arm, g', of the bracket is arranged an adjustingscrew, g2, the tip. of which bears against the spring-arm G. l

In the present instance the diaphragm A is supposed to be of metal, and to it is connected 7o one of the terminals, l, of abatterycircuit,the other terminal, Z', of which is connected with a metallic plug, p, which extends through the bottom of cup E, said circuit preferably including the primary helix of an induction-coil, I, the secondary helix of which is to be connected with the line-wire and ground in the usualmanner. I The cup E is to be filled with mercury, as indicated by M, beforeplacing on the top, the screw F being iirst screwed outward until its tip is flush, Vor nearly so, with the inner surface of the bottom ofthe cup. The screw gl is then screwed in to adjust the cup `upward until the carbon button D nearly touches the button D on thel diaphragm, and then the screw F is screwed inward, displacing a portion of the mercury and forcing the mass of mercury within the cup upward against the top e until said top is bowed upward sufficiently to 'bring the button D directly in contactwth the-button D. Connection will then be completed from the circuit-terminal Z to the terminal Z through the diaphragm A, the carbon button D, carbon button D', the mercury in the cup E, and the metallic plug p. When sounds or sound-waves are projected against the dia phragm, the consequent vibrations of the latter cause a variation of contact-pressure between the buttons D and D, the tension of the plate roo supporting the latter being so regulated by the in which case the electrode would be connected directly With one ofthe battery-circuit terminals in any Well-known manner. The use of the liquid thus confined, and so that its pressure upon the plate may be regulated, renders possible a fine adjustment of the electrodes and the transmission of both loW and loud tones without those sudden breakages of the circuit, which frequently occur when theliquid is unconfined.

What I claim is- 1. In a telephonie transmitter, the combination,with a variable contact-electrode, of a body of mercury confined and under pressure and in contact with said electrode, substantially as and its supporting elastic plate, substantially as described.

3. In a telephonic transmitter, the combination of one electrode supported and controlled by a diaphragm, a confined body of liquid whose confining-surface contains and controls a second electrode, which body of liquid is adapted to vary and control the position ofthe second electrode, land means for varying the pressure of said body of liquid, so as to vary and control the position of the second electrode, substantially as described.

4. In a telephonie transmitter of the class referred to, the combination, with one of the variable contact-electrodes, of an elastic plate containing and supporting such electrode and a vessel adapted to contain a body of liquid, the elastic plate forming the cover thereto, the liquid therein serving the purpose of adjusting the pressure upon such plate and its tension, substantially as described. l

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

CHARLES A. RANDALL.

Vitnesses:

J AMES L. Nonnrs,

ALBERT H. NoRRIs. 

